1. Field of the Invention
One embodiment of the present invention relates to a lighting device and a light-emitting device which include a light-emitting member exhibiting electroluminescence (EL) and also relates to a manufacturing apparatus with which the lighting device and the light-emitting device are manufactured.
2. Description of the Related Art
A light-emitting element containing organic compounds as a luminous body has been expected to be applied to next-generation lighting. The light-emitting element containing organic compounds as a luminous body has features such as drive at a low voltage with low power consumption.
An EL layer included in a light-emitting element includes at least a light-emitting layer. The EL layer can have a layered structure including a hole injection layer, a hole transport layer, an electron transport layer, an electron injection layer, and/or the like, in addition to the light-emitting layer.
It is said that, as for a light-emitting mechanism of a light-emitting element, an EL layer is interposed between a pair of electrodes and voltage is applied to the EL layer, so that electrons injected from a cathode and holes injected from an anode are recombined in an emission center of the EL layer to form molecular excitons, and the molecular excitons release energy when returning to a ground state; thus, light is emitted. Singlet excitation and triplet excitation are known as excited states, and light emission can probably be achieved through either of the excited states.
Further, since the pair of electrodes and the light-emitting layer are formed as films in such a light-emitting element, surface light emission can easily be obtained by forming a large-area light-emitting element. This is a feature which is hard to obtain in light sources such as incandescent lamps and LEDs (point light sources) or in fluorescent lamps (line light sources), so that the above light-emitting element has a high utility value as a light source such as lighting.
A light-emitting element using an organic compound as a luminous body, which has features such as thinness, lightness, high-speed response, and DC drive at a low voltage, is expected to be applied to a next-generation flat panel display. In particular, a display device in which light-emitting elements are arranged in a matrix has advantages of a wide viewing angle and excellent visibility.
Recently, in order to achieve a display capable of full-color display, various structures have been proposed. For example, structures have been examined, such as a structure for performing full-color display by combination of a white light-emitting element and a color filter and a structure for performing full-color display by arrangement of three light-emitting layers of a light-emitting layer exhibiting a red color, a light-emitting layer exhibiting a green color, and a light-emitting layer exhibiting a blue color.
An organic light-emitting device constituted by a pixel group having pixels of four colors of red, green, blue, and white is disclosed in Patent Document 1.
A full-color display device in which a light-emitting device has a plurality of EL elements emitting light of different colors and at least one of the EL elements has a triplet compound and the other EL elements have a singlet compound is disclosed in Patent Document 2.